gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright 1987, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GAS, the GNU Assembler.
   7
   8    GAS is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2, or (at your option)
  11    any later version.
  12
  13    GAS is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with GAS; see the file COPYING.  If not, write to the Free
  20    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  21    02110-1301, USA.  */
  22
  23 /* Segments & sub-segments.  */
  24
  25 #include "as.h"
  26
  27 #include "subsegs.h"
  28 #include "obstack.h"
  29
  30 frchainS *frchain_now;
  31
  32 static struct obstack frchains;
  33
  34 static fragS dummy_frag;
  35
  36 \f
  37 void
  38 subsegs_begin (void)
  39 {
  40   obstack_begin (&frchains, chunksize);
  41 #if __GNUC__ >= 2
  42   obstack_alignment_mask (&frchains) = __alignof__ (frchainS) - 1;
  43 #endif
  44
  45   frchain_now = NULL;           /* Warn new_subseg() that we are booting.  */
  46   frag_now = &dummy_frag;
  47 }
  48 \f
  49 /*
  50  *                      subseg_change()
  51  *
  52  * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
  53  * subsegment. If we are already in the correct subsegment, change nothing.
  54  * This is used eg as a worker for subseg_set [which does make a new frag_now]
  55  * and for changing segments after we have read the source. We construct eg
  56  * fixSs even after the source file is read, so we do have to keep the
  57  * segment context correct.
  58  */
  59 void
  60 subseg_change (register segT seg, register int subseg)
  61 {
  62   segment_info_type *seginfo = seg_info (seg);
  63   now_seg = seg;
  64   now_subseg = subseg;
  65
  66   if (! seginfo)
  67     {
  68       seginfo = (segment_info_type *) xmalloc (sizeof (*seginfo));
  69       memset ((PTR) seginfo, 0, sizeof (*seginfo));
  70       seginfo->fix_root = NULL;
  71       seginfo->fix_tail = NULL;
  72       seginfo->bfd_section = seg;
  73       seginfo->sym = 0;
  74       bfd_set_section_userdata (stdoutput, seg, (PTR) seginfo);
  75     }
  76 }
  77 \f
  78 static void
  79 subseg_set_rest (segT seg, subsegT subseg)
  80 {
  81   frchainS *frcP;               /* crawl frchain chain */
  82   frchainS **lastPP;            /* address of last pointer */
  83   frchainS *newP;               /* address of new frchain */
  84   segment_info_type *seginfo;
  85
  86   mri_common_symbol = NULL;
  87
  88   if (frag_now && frchain_now)
  89     frchain_now->frch_frag_now = frag_now;
  90
  91   assert (frchain_now == 0
  92           || frchain_now->frch_last == frag_now);
  93
  94   subseg_change (seg, (int) subseg);
  95
  96   seginfo = seg_info (seg);
  97
  98   /* Attempt to find or make a frchain for that subsection.
  99      We keep the list sorted by subsection number.  */
 100   for (frcP = *(lastPP = &seginfo->frchainP);
 101        frcP != NULL;
 102        frcP = *(lastPP = &frcP->frch_next))
 103     if (frcP->frch_subseg >= subseg)
 104       break;
 105
 106   if (frcP == NULL || frcP->frch_subseg != subseg)
 107     {
 108       /* This should be the only code that creates a frchainS.  */
 109
 110       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 111       newP->frch_subseg = subseg;
 112       newP->fix_root = NULL;
 113       newP->fix_tail = NULL;
 114       obstack_begin (&newP->frch_obstack, chunksize);
 115 #if __GNUC__ >= 2
 116       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 117 #endif
 118       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 119       newP->frch_frag_now->fr_type = rs_fill;
 120       newP->frch_cfi_data = NULL;
 121
 122       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 123
 124       *lastPP = newP;
 125       newP->frch_next = frcP;
 126       frcP = newP;
 127     }
 128
 129   frchain_now = frcP;
 130   frag_now = frcP->frch_frag_now;
 131
 132   assert (frchain_now->frch_last == frag_now);
 133 }
 134
 135 /*
 136  *                      subseg_set(segT, subsegT)
 137  *
 138  * If you attempt to change to the current subsegment, nothing happens.
 139  *
 140  * In:  segT, subsegT code for new subsegment.
 141  *      frag_now -> incomplete frag for current subsegment.
 142  *      If frag_now==NULL, then there is no old, incomplete frag, so
 143  *      the old frag is not closed off.
 144  *
 145  * Out: now_subseg, now_seg updated.
 146  *      Frchain_now points to the (possibly new) struct frchain for this
 147  *      sub-segment.
 148  */
 149
 150 segT
 151 subseg_get (const char *segname, int force_new)
 152 {
 153   segT secptr;
 154   segment_info_type *seginfo;
 155   const char *now_seg_name = (now_seg
 156                               ? bfd_get_section_name (stdoutput, now_seg)
 157                               : 0);
 158
 159   if (!force_new
 160       && now_seg_name
 161       && (now_seg_name == segname
 162           || !strcmp (now_seg_name, segname)))
 163     return now_seg;
 164
 165   if (!force_new)
 166     secptr = bfd_make_section_old_way (stdoutput, segname);
 167   else
 168     secptr = bfd_make_section_anyway (stdoutput, segname);
 169
 170   seginfo = seg_info (secptr);
 171   if (! seginfo)
 172     {
 173       secptr->output_section = secptr;
 174       seginfo = (segment_info_type *) xmalloc (sizeof (*seginfo));
 175       memset ((PTR) seginfo, 0, sizeof (*seginfo));
 176       seginfo->fix_root = NULL;
 177       seginfo->fix_tail = NULL;
 178       seginfo->bfd_section = secptr;
 179       bfd_set_section_userdata (stdoutput, secptr, (PTR) seginfo);
 180       seginfo->frchainP = NULL;
 181       seginfo->lineno_list_head = seginfo->lineno_list_tail = NULL;
 182       seginfo->sym = NULL;
 183       seginfo->dot = NULL;
 184     }
 185   return secptr;
 186 }
 187
 188 segT
 189 subseg_new (const char *segname, subsegT subseg)
 190 {
 191   segT secptr;
 192
 193   secptr = subseg_get (segname, 0);
 194   subseg_set_rest (secptr, subseg);
 195   return secptr;
 196 }
 197
 198 /* Like subseg_new, except a new section is always created, even if
 199    a section with that name already exists.  */
 200 segT
 201 subseg_force_new (const char *segname, subsegT subseg)
 202 {
 203   segT secptr;
 204
 205   secptr = subseg_get (segname, 1);
 206   subseg_set_rest (secptr, subseg);
 207   return secptr;
 208 }
 209
 210 void
 211 subseg_set (segT secptr, subsegT subseg)
 212 {
 213   if (! (secptr == now_seg && subseg == now_subseg))
 214     subseg_set_rest (secptr, subseg);
 215   mri_common_symbol = NULL;
 216 }
 217
 218 #ifndef obj_sec_sym_ok_for_reloc
 219 #define obj_sec_sym_ok_for_reloc(SEC)   0
 220 #endif
 221
 222 symbolS *
 223 section_symbol (segT sec)
 224 {
 225   segment_info_type *seginfo = seg_info (sec);
 226   symbolS *s;
 227
 228   if (seginfo == 0)
 229     abort ();
 230   if (seginfo->sym)
 231     return seginfo->sym;
 232
 233 #ifndef EMIT_SECTION_SYMBOLS
 234 #define EMIT_SECTION_SYMBOLS 1
 235 #endif
 236
 237   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 238     {
 239       /* Here we know it won't be going into the symbol table.  */
 240       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 241     }
 242   else
 243     {
 244       segT seg;
 245       s = symbol_find (sec->symbol->name);
 246       /* We have to make sure it is the right symbol when we
 247          have multiple sections with the same section name.  */
 248       if (s == NULL
 249           || ((seg = S_GET_SEGMENT (s)) != sec
 250               && seg != undefined_section))
 251         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 252       else if (seg == undefined_section)
 253         {
 254           S_SET_SEGMENT (s, sec);
 255           symbol_set_frag (s, &zero_address_frag);
 256         }
 257     }
 258
 259   S_CLEAR_EXTERNAL (s);
 260
 261   /* Use the BFD section symbol, if possible.  */
 262   if (obj_sec_sym_ok_for_reloc (sec))
 263     symbol_set_bfdsym (s, sec->symbol);
 264   else
 265     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 266
 267   seginfo->sym = s;
 268   return s;
 269 }
 270
 271 /* Return whether the specified segment is thought to hold text.  */
 272
 273 int
 274 subseg_text_p (segT sec)
 275 {
 276   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
 277 }
 278
 279 /* Return non zero if SEC has at least one byte of data.  It is
 280    possible that we'll return zero even on a non-empty section because
 281    we don't know all the fragment types, and it is possible that an
 282    fr_fix == 0 one still contributes data.  Think of this as
 283    seg_definitely_not_empty_p.  */
 284
 285 int
 286 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 287 {
 288   segment_info_type *seginfo = seg_info (sec);
 289   frchainS *chain;
 290   fragS *frag;
 291
 292   if (!seginfo)
 293     return 0;
 294
 295   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 296     {
 297       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 298         if (frag->fr_fix)
 299           return 1;
 300       if (obstack_next_free (&chain->frch_obstack)
 301           != chain->frch_last->fr_literal)
 302         return 1;
 303     }
 304   return 0;
 305 }
 306
 307 void
 308 subsegs_print_statistics (FILE *file)
 309 {
 310   frchainS *frchp;
 311   asection *s;
 312
 313   fprintf (file, "frag chains:\n");
 314   for (s = stdoutput->sections; s; s = s->next)
 315     {
 316       segment_info_type *seginfo;
 317
 318       /* Skip gas-internal sections.  */
 319       if (segment_name (s)[0] == '*')
 320         continue;
 321
 322       seginfo = seg_info (s);
 323       if (!seginfo)
 324         continue;
 325
 326       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 327         {
 328           int count = 0;
 329           fragS *fragp;
 330
 331           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 332             count++;
 333
 334           fprintf (file, "\n");
 335           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 336                    segment_name (s), count);
 337         }
 338     }
 339 }
 340
 341 /* end of subsegs.c */